Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Institutes of Health, Bethesda, Maryland, United States of America.
PLoS One. 2013 Sep 6;8(9):e71427. doi: 10.1371/journal.pone.0071427. eCollection 2013.
Thioredoxin (Trx) and thioredoxin reductase 1 (TR1) are among the major redox regulators in mammalian cells and have a wide variety of roles, including removal of intracellular reactive oxygen species (ROS) and prevention of cell death. Tumor necrosis factor-α (TNF-α) induces cancer cell death. Although ROS have been proposed to participate in this process, the role of the thioredoxin system in TNF-α stimulated cell death remains unclear. We investigated the possibility that the thioredoxin system protects against TNF-α-induced cancer cell death by examining whether TR1/Trx1 status controls TNF-α-induced apoptosis in EMT6 murine breast cancer cells. TR1-deficient cells were more sensitive to TNF-α than control cells. Increased sensitivity to TNF-α was most pronounced in Trx1-deficient cells. TNF-α-induced nuclear localization of phosphorylated ERK 1/2 (p-ERK 1/2) correlated with increased apoptosis in TR1- and Trx1-deficient cells, suggesting a pro-apoptotic role for nuclear p-ERK 1/2 in TNF-α-induced apoptosis. In addition, phosphoinositide 3-kinase (PI3K) inhibition dramatically reduced TNF-α-stimulated apoptosis and nuclear localization of p-ERK 1/2. In contrast, inhibition of ROS, MEK, JNK, or p38 did not significantly alter p-ERK 1/2 localization or apoptosis in TR1- and Trx1-deficient cells compared to control cells. Further, NF-κB p65 localization was not changed in TR1- and Trx1-deficient cells in response to TNF-α relative to control cells. Our data suggest that the thioredoxin system plays a critical role in protecting against TNF-α-induced apoptosis by regulating the levels of nuclear p-ERK 1/2 in a PI3K-dependent manner.
硫氧还蛋白 (Trx) 和硫氧还蛋白还原酶 1 (TR1) 是哺乳动物细胞中主要的氧化还原调节剂之一，具有多种作用，包括清除细胞内的活性氧 (ROS) 和防止细胞死亡。肿瘤坏死因子-α (TNF-α) 诱导癌细胞死亡。虽然 ROS 被认为参与了这一过程，但硫氧还蛋白系统在 TNF-α 刺激的细胞死亡中的作用尚不清楚。我们通过研究 TR1/Trx1 状态是否控制 EMT6 鼠乳腺癌细胞中 TNF-α 诱导的细胞凋亡，来研究硫氧还蛋白系统是否通过防止 TNF-α 诱导的细胞死亡来发挥作用。与对照细胞相比，TR1 缺陷细胞对 TNF-α 更为敏感。在 Trx1 缺陷细胞中，对 TNF-α 的敏感性增加最为明显。TNF-α 诱导的磷酸化 ERK 1/2 (p-ERK 1/2) 的核定位与 TR1 和 Trx1 缺陷细胞中凋亡的增加相关，这表明核 p-ERK 1/2 在 TNF-α 诱导的凋亡中具有促凋亡作用。此外，磷酸肌醇 3-激酶 (PI3K) 抑制显著降低了 TNF-α 刺激的细胞凋亡和 p-ERK 1/2 的核定位。相比之下，与对照细胞相比，ROS、MEK、JNK 或 p38 的抑制并未显著改变 TR1 和 Trx1 缺陷细胞中 p-ERK 1/2 的定位或凋亡。此外，与对照细胞相比，TR1 和 Trx1 缺陷细胞中 NF-κB p65 的定位在 TNF-α 刺激下没有改变。我们的数据表明，硫氧还蛋白系统通过 PI3K 依赖性方式调节核 p-ERK 1/2 的水平，在防止 TNF-α 诱导的细胞凋亡中起着关键作用。
